function BigImage(){
    var screenImage = $("img");
    var theImage = new Image();
    theImage.src = screenImage.attr("src");
    var imageWidth = theImage.width;
    var imageHeight = theImage.height;
}
$("img").on('click',function(){
    var theImage = new Image();
    theImage.src = $(this).attr("src");
    var imageWidth = theImage.width>500?500:theImage.width;
    var imageHeight = theImage.height>500?500:theImage.height;
    $("#showImg").find("img").attr("src" , theImage.src).css({width:imageWidth,height:imageHeight,marginLeft:-imageWidth/2});
    $("#showImg").show();
});
$("#showImg").on('click',function(){
    $("#showImg").hide();
});